> Yahoo!, for example, has as many users as Google - or thereabouts - but is a
> lot less successful at monetising them.
Because of incompetence.
I was a subscriber to a couple of Yahoo Groups, but the way Yahoo reformats the mails from these groups caused my spamfilter to bounce them, causing Yahoo to suspend my group membership. This happened over and over again, until I gave up reactivating my membership.
Then, in another Yahoo hosted group, they allowed a spammer to repeatedly spam the group, over several months. So, eventually I unsubscribed.
Google however seem to be able to forward an email without turning it in into spam. And they are able to block spammers pretty effectively.
So, IMO, Yahoo will lose due to their own incompetence.
Now. if MS are dumb enough to start serving ads from the OS, then that'll be the final victory of open source software.